This ENCODE consortium project aims to identify and classify chromatin regulatory elements in the human genome in systematic fashion. This goal is being pursued through the application of chromatin methods and ultra high-throughput sequencing to acquire genomewide maps that reflect the distributions of histone modifications and chromatin proteins in a given cell type. By assaying multiple cell types, the project will build an increasingly comprehensive catalog of chromatin regulatory elements and gain insight into their cell typespecificities. Although there are dozens of different modifications and many other structural components in chromatin, only a fraction can be measured with existing antibodies and reagents. The rationale of this supplement request is that an ability to characterize these additional modifications and proteins as they occur across the genome would augment our understanding of the structure and regulation of functional elements elucidated by ENCODE, and reveal additional elements of yet unknown significance. Requested funds would be use to screen dozens of additional chromatin epitopes with the goal of identifying suitable reagents and methods for genomewide mapping. The screens will be pursued through a combination of conventional methods and high-throughput techniques. Reagents identified through this process will then be applied within the existing ENCODE pipeline to characterize genomewide distributions of the novel epitopes and their relationships to known or novel regulatory elements. Chromatin regulation is of wide-ranging importance in human development and disease. The proposed systematic identification and characterization of chromatin regulatory elements in the human genome will offer valuable insight into the structure and function of chromatin, and provide a resource for investigators in chromatin, genomics, cancer and many other fields of research. All data collected in the context of the proposed project will be made available pre-publication to the greater scientific community as soon as reliability has been confirmed. 2.